JPH05200947A - Gas barrier laminated film - Google Patents

Abstract

PURPOSE:To provide a gas barrier laminated film enhanced in the bonding strength with an ethylene/vinyl alcohol copolymer or polyvinyl alcohol, little in the use amount of an org. solvent at the time of production and capable of being produced at molding temp. of 300 deg.C or lower in the case of the production due to extrusion laminate molding. CONSTITUTION:A laminated film is obtained by laminating a resin having an acid or acid anhydride group to at least the single surface of an ethylene/ vinyl alcohol copolymer or polyvinyl alcohol film through a membrane of a silane coupling agent having an amino group at its terminal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated film having a high gas barrier property, capable of retorting, and having excellent adhesiveness, microwave oven suitability and transparency, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a plastic film such as polyamide, polypropylene, or cellophane coated with polyvinylidene chloride (hereinafter abbreviated as PVDC) has been widely used as a packaging material requiring a gas barrier property. In addition, as a material having a higher gas barrier property, aluminum (hereinafter referred to as Al
Has also been used as a gas barrier material in the form of foil or vapor deposited layer. These are used differently depending on the application, but the plastic film coated with PVDC has a relatively low gas barrier property, and changes color to yellow with the passage of time, impairing the aesthetics of the contents and giving a yellowish back printing. I can see it. Although Al has an excellent gas barrier property, it is opaque and thus lacks visibility of the contents. Further, since it is a metal, it cannot be heated in a microwave oven.

For these materials, a laminated plastic film using an ethylene-vinyl alcohol copolymer (hereinafter abbreviated as EVOH) or polyvinyl alcohol (hereinafter abbreviated as PVA) is disclosed in, for example, JP-A-02-3284.
6, JP-A-02-45377 and the like. EV
OH and PVA have excellent gas barrier properties and aroma retention properties, are transparent, and have retort resistance and microwave oven suitability. But E
Since VOH and PVA have a high melting point of 160 ° C. or higher, they have poor heat sealability.

Therefore, when it is used as a packaging material, polyolefins are laminated and used.
There is a problem that the adhesiveness between A and the polyolefin is low.
As an improvement method, JP-A-02-32846 discloses a method of improving adhesiveness with a polyolefin by using a polyester adhesive. However, since a polyester-based adhesive is used, a large amount of organic solvent is required, which is not preferable in terms of environmental hygiene, and initial adhesion is weak, and thus aging at 40 ° C. for about 2 days after molding is required. Further, in Japanese Patent Laid-Open No. 02-293138, a polyolefin and an adhesive resin are coextruded to produce E
A method for bonding VOH and polyolefin is shown. However, in the method of adhering the polyolefin layer and the EVOH layer with the resin layer having adhesiveness, the adhesive layer is thicker and a large amount of adhesive resin is required as compared with the case of using the adhesive solution. Further, since the surface printing is inevitable, the printing durability is poor. Further, when the bonding of EVOH or PVA and polyolefin is carried out by the extrusion laminating method,
In order to improve the adhesiveness, it is necessary to perform the molding at a temperature of 300 ° C. or higher, and the molding cost is high, and it is accompanied by smoke and odor, which is not preferable in terms of environmental hygiene, and yet good adhesiveness cannot be obtained.

[0005]

DISCLOSURE OF THE INVENTION The present invention has a high initial adhesive strength, uses a small amount of an organic solvent during production, and can be produced at a forming temperature of 300 ° C. or lower when produced by extrusion lamination molding. An object of the present invention is to obtain a laminated film having high adhesiveness between a PVA film and a resin layer and a method for producing the laminated film.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has found that a silane coupling agent having an amino group at the terminal and a resin having a carboxyl group, a metal carboxylate group or an acid anhydride group. It was found that the EVOH or PVA film and the resin layer can be firmly bonded to each other by using and, and the present invention has been completed.

That is, the above-mentioned problems are caused by EVOH or P
Laminated film in which a resin having a carboxyl group, a metal carboxylate group or an acid anhydride group is laminated on at least one surface of a VA film via a thin layer of a silane coupling agent having an amino group at the end, and a method for producing the same. Will be resolved.

The EVOH film in the present invention is obtained by saponifying an ethylene-vinyl acetate copolymer, and the composition and saponification degree of the copolymer are not limited as long as it has a gas barrier property. If necessary, these may be subjected to stretching or treatment such as addition of various additives such as antistatic agents and lubricants. Similarly, the PVA film may also be subjected to treatments such as stretching and addition of additives.
Although the thickness is not particularly limited, it is preferably 5 to 100 μm in consideration of easy handling as a film.

As the silane coupling agent having an amino group at the terminal in the present invention, γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β- (aminoethyl ) -Γ-aminopropylmethyldimethoxysilane and the like.

These silane coupling agents may be diluted with a solvent, applied onto an EVOH or PVA film by a known method such as a gravure coater, and then dried to form a thin layer of the silane coupling agent. In addition, stabilizers and other additives may be added if necessary.

As the solvent for the silane coupling agent,
Water, methanol, ethanol, 2-propanol, etc. are suitable, and these can also be mixed and used. The concentration of the silane coupling agent varies depending on the solvent, but is usually 0.01 to 5%, preferably 0.1 to 2%.

Drying can be carried out by a known method such as blowing hot air or using a heating roll. The drying temperature is preferably 50 ° C. to 90 ° C., though it varies depending on the solvent, the concentration, and the drying time. If the temperature is 50 ° C. or lower, the drying time is too long to be practical, and if the temperature is 90 ° C. or higher, the printing pitch shift becomes large.

The resin having a carboxyl group, a metal carboxylate group or an acid anhydride group in the present invention is an olefin polymer containing a carboxyl group, a metal carboxylate group or an acid anhydride group in the molecule. The olefin polymer as used herein includes an olefin homopolymer, an olefin copolymer, and a mixture thereof. The olefin is not particularly limited, for example ethylene,
Propylene, butene-1, hexene-1, octene-
Examples thereof include 1,4-methylpentene-1, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, vinyl acetate, acrylic acid and methacrylic acid.

As a method of introducing a carboxyl group, a carboxylic acid metal base or an acid anhydride group into the molecule of an olefin polymer, a radically polymerizable carboxylic acid, a carboxylic acid metal salt or an acid anhydride is used when an olefin is polymerized. There is a method of copolymerizing a compound, a method of graft-copolymerizing a radically polymerizable carboxylic acid, a carboxylic acid metal salt or an acid anhydride with an olefin polymer using a radical initiator such as an organic peroxide. Any resin having a carboxyl group, a metal carboxylate group or an acid anhydride group produced by these methods can be preferably used in the present invention. In addition to carboxylic acid, carboxylic acid metal salt or acid anhydride, olefin is further copolymerized with 3
It may be a multi-component copolymer composed of components or more. Examples of the comonomer here include methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, vinyl acetate, acrylic acid, methacrylic acid and the like.

Specific examples of the radical-polymerizable carboxylic acid, carboxylic acid metal salt or acid anhydride include maleic acid, itaconic acid, citraconic acid, dodecenyl succinic acid, and their metal salts and anhydrides. .. Depending on the case, it is possible to use two or more of them together.

Further, these resins having a carboxyl group, a metal carboxylate group or an acid anhydride group can be used as a mixture with other resins as long as the adhesiveness can be maintained. If desired, stabilizers, lubricants, antistatic agents, pigments, fillers and other additives may be added.

The resin having a carboxyl group, a metal carboxylate group or an acid anhydride group can be laminated on the thin layer of the silane coupling agent having an amino group at the terminal by a known method such as extrusion lamination. .. When a resin layer having a carboxyl group, a metal carboxylate group or an acid anhydride group is provided by the extrusion laminating method, equipment such as a gravure coater is used in advance to prepare a silane cup having an amino group at the end on the EVOH or PVA film. The ring agent diluted solution can be applied and dried, and then a resin layer having a carboxyl group, a metal carboxylate group or an acid anhydride group can be laminated using a general extrusion laminating machine. If an extrusion laminating machine with an anchor coater is used, it is possible to laminate a silane coupling agent having an amino group at the end and a resin layer having a carboxyl group, a metal carboxylate group or an acid anhydride group in a single step. it can. The resin temperature in extrusion lamination is 300 ° C or lower, preferably 200 to 270 ° C. In the present invention, the silane coupling agent having an amino group at the end can be diluted with water, so that the amount of the organic solvent used can be significantly reduced as compared with the conventional adhesive.

Further, in the present invention, it is not yet clear by what effect the strong adhesive strength is exhibited immediately after molding. However, since the silane coupling agent having an amino group at the terminal has a functional group capable of chemically reacting with both the EVOH or PVA film and the resin having a carboxyl group, a metal carboxylate group or an acid anhydride group, The reaction seems to be a major factor in adhesion.

[0019]

The present invention will be described in more detail with reference to Examples and Comparative Examples. Example 1 (Production of Resin Having Acid Anhydride Group) A copolymer of ethylene and maleic anhydride was produced using a high-pressure polyethylene production facility having an autoclave type reactor. The obtained copolymer had an MFR (190 ° C.) of 8.6 g / 10 minutes and a unit derived from maleic anhydride of 2.2% by weight. The copolymer composition was determined by infrared absorption spectrum. (Production of Laminate) Commercially available EVOH film (“Eval” EF-F manufactured by Kuraray Co., Ltd., width 630 mm, thickness 15 μm)
m) was laminated with a thin layer of a silane coupling agent having an amino group at the terminal by an extrusion laminating machine equipped with an anchor coat device, and further a resin layer having an acid anhydride group was laminated. A commercially available γ-aminopropyltriethoxysilane is used as the silane coupling agent having an amino group at the terminal, and 24 g of γ-aminopropyltriethoxysilane is used.
12 kg of water and 12 kg of ethanol were mixed to obtain a concentration of 0.
A 1% by weight solution was prepared. Extrusion laminating machine
An extruder having a diameter of 90 mm and a roll surface width of 1300 mm was used. The molding conditions are 2 g / m ² (wet) coating amount of the anchor coater, 80 ° C. drying temperature and 100 m molding speed.
/ Min, the laminate thickness was 25 μm, the slit width of the die was 0.8 mm, and the resin temperature immediately below the die was 217 ° C. (Evaluation) The amount of organic solvent used was calculated from the concentration and the coating amount. Since the coating amount is 2 g / m ² and the ethanol concentration is 50%, the amount of the organic solvent used is 1 g / m ² . The peel strength was evaluated twice immediately after molding the laminate and twice after aging at 40 ° C. for 2 days. Width 1 in the flow direction of molding
The strip strength was measured when the strip was cut into a strip of 5 mm and stripped 180 ° at a speed of 300 mm / min. The evaluation results are shown in Table 1.

Example 2 The copolymer of ethylene and maleic anhydride obtained in Example 1 was treated with MFR (190 ° C.) of 21.0 g / 10 minutes and a density of 0.9.
High-pressure polyethylene of 17 g / cm ³ and 30/7
The mixture was mixed so that the weight ratio was 0. When mixing,
Both were dry blended with a tumbler, and then melt-kneaded at 170 ° C. using a 40 mmφ single screw extruder to form pellets. MFR (190 ℃) of the mixture is 14.0g / 10
The unit derived from maleic anhydride was 0.6% by weight. Extrusion lamination molding and evaluation were performed in the same manner as in Example 1 except that this resin was used as the resin having an acid anhydride group. The evaluation results are shown in Table 1.

Example 3 A terpolymer of ethylene, ethyl acrylate and maleic anhydride was produced using a high-pressure polyethylene production facility having an autoclave type reactor. The obtained copolymer had an MFR (190 ° C.) of 32 g / 10 minutes, a maleic anhydride-derived unit of 2.9% by weight, and an ethyl acrylate-derived unit of 10.6% by weight. Example 1 except that this terpolymer was used as the resin having an acid anhydride group.
Extrusion lamination molding and evaluation were performed in the same manner as in. The evaluation results are shown in Table 1.

Example 4 MFR (190 ° C.) 21.0 g / 10 minutes, density 0.917
0.5% by weight of maleic anhydride and 0.01% by weight of dicumyl peroxide in high-pressure polyethylene of g / cm ^3.
Is mixed with a tumbler, and is mixed with a φ40 mm single-screw extruder to 25
It was denatured and pelletized at 0 ° C. The obtained modified polyethylene had an MFR (190 ° C.) of 13.0 g / 10 minutes and a unit derived from maleic anhydride of 0.35% by weight. Extrusion lamination molding and evaluation were performed in the same manner as in Example 1 except that this modified polyethylene was used as the resin having an acid anhydride group. The evaluation results are shown in Table 1.

Example 5 Extrusion laminate molding and evaluation were carried out in the same manner as in Example 1 except that commercially available N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane was used as the silane coupling agent. The evaluation results are shown in Table 1.

Example 6 As a resin having a carboxyl group, MFR (190
° C.) 8.0 g / 10 min, density 0.930 g / cm ^3, the unit 9.0 wt% of ethylene derived from methacrylic acid - except for using a methacrylic acid copolymer in the same manner as in Example 1 extrusion lamination molding And evaluated. The evaluation results are shown in Table 1.

Comparative Example 1 Extrusion lamination and evaluation were carried out in the same manner as in Example 1 except that a resin having an acid anhydride group was extrusion laminated directly on one surface of the EVOH film without using a silane coupling agent. The evaluation results are shown in Table 1.

Comparative Example 2 Extrusion lamination molding and evaluation were carried out in the same manner as in Example 1 except that a commercially available γ-methacryloxypropyltrimethoxysilane was used as a silane coupling agent having no amino group at the terminal. The evaluation results are shown in Table 1.

Comparative Example 3 MFR (190 ° C.) was used instead of the resin having an acid anhydride group.
Extrusion laminate molding and evaluation were carried out in the same manner as in Example 1 except that high-pressure polyethylene was used with a density of 21.0 g / 10 minutes and a density of 0.917 g / cm ³ . The evaluation results are shown in Table 1.

Comparative Example 4 Extrusion lamination molding and evaluation were performed in the same manner as in Example 1 except that the high-pressure polyethylene of Comparative Example 3 was used and extrusion lamination was performed at a resin temperature of 305 ° C. immediately below the die. The evaluation results are shown in Table 1.

Comparative Example 5 An EVOH film and a commercially available high-pressure polyethylene film were bonded by dry lamination using a urethane adhesive. The results are shown in Table 1.

[0030]

[Table 1]

[0031]

The adhesive strength between the EVOH or PVA film and the resin layer is strong from the beginning, the amount of the organic solvent used is small at the time of production, and the adhesiveness is good when produced by extrusion laminating molding. A laminated film which can be produced at the following molding temperatures was obtained.

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Claims (3)

[Claims] 1. An ethylene-vinyl alcohol copolymer,
Alternatively, a laminated film in which a resin having a carboxyl group, a metal carboxylate group or an acid anhydride group is laminated on at least one surface of a polyvinyl alcohol film via a thin layer of a silane coupling agent having an amino group at a terminal. 2. An ethylene-vinyl alcohol copolymer,
Alternatively, on at least one surface of the polyvinyl alcohol film, after coating and drying a solution of a silane coupling agent having an amino group at the terminal, a carboxyl group, a resin layer having a carboxylate metal base or an acid anhydride group is provided. Method for producing a laminated film. 3. The method for producing a laminated film according to claim 2, wherein an extrusion laminating method is used as a method for providing a resin layer having a carboxyl group, a metal carboxylate group or an acid anhydride.